Conventionally, there is provided a remote monitoring control system in which a transmission processing device, an operation terminal device and a control terminal device are connected by two signal lines (see, e.g., Japanese Unexamined Patent Application Publication No. 2001-86577). In the remote monitoring control system, specific addresses are respectively allotted to the operation terminal device and the control terminal device.
The operation terminal device includes a plurality of switches. As the states of the switches are changed, e.g., by pressing the switches, the operation terminal device transmits the information as operation data to the transmission processing device.
The transmission processing device gains access to each of the operation terminal device and the control terminal device and receives operation data from the operation terminal device. Furthermore, the transmission processing device transmits control data to the control terminal device which is previously associated, by an address, with the operation terminal device that has generated the operation data.
The control terminal device includes relays provided therein. Upon receiving the control data from the transmission processing device, the control terminal device turns on or off the relays, thereby controlling loads, such as a lighting device and a surveillance camera.
Each of the operation terminal device and the control terminal device includes, e.g., a transceiver circuit unit for transmitting and receiving a transmission signal or the like, a terminal processing unit for monitoring the operation states of the switches and executing control of the relays, and a synthetic-resin-made device housing. The terminal processing unit, the transceiver circuit unit and display elements are realized by, e.g., mounting an integrated circuit on a printed wiring board.
Switches, light emitting diodes (LEDs) as display elements, and so forth are mounted on the printed wiring board of the operation terminal device. As the display elements, there are provided two kinds of display elements, namely a red LED which indicates the turn-on of each of the switches and a green LED which indicates the turn-off of each of the switches. If the switches are pressed, the display elements are turned on or off in a corresponding relationship with the control states of the loads connected to the control terminal device. The switches and the loads are associated with each other by the transmission processing device.
Discrete parts are used as the two kinds of the display elements. The display elements are soldered to the printed wiring board.
The device housing includes a body, a lid, a decoration cover, and a nameplate. The nameplate is ultrasonically bonded to the front surface of the decoration cover. The decoration cover is attached to the outside of the lid. The tip portions of the two kinds of display elements are inserted into insertion holes formed in a bottom wall of the lid of the device housing.
In the operation terminal device of the remote monitoring control system disclosed in Japanese Unexamined Patent Application Publication No. 2001-86577, the discrete-type display elements are mounted on the printed wiring board. The lead portions of the display elements are mounted by manual soldering. Thus, the work efficiency is poor. In the operation terminal device disclosed in Japanese Unexamined Patent Application Publication No. 2001-86577, it is thinkable to change the discrete-type display elements to surface-mount-type display elements. However, the surface-mount-type display elements are less distant from a mounting surface than the discrete-type display elements. That is to say, the distance from the light emission surfaces of the display elements to the front surface of the device housing becomes longer. This makes it difficult to enhance the visibility of the display elements.